Semiconductor processing equipment for the processing of semiconductor substrates is typically placed in a clean room because clean, dust free processing is required. At the front side of the system, facing the clean room, substrate cassettes with wafers to be processed are received and substrate cassette handling and storage equipment and wafer handling equipment is typically provided. At the rear side of the system the processing chamber is provided and at the extreme end opposite to the clean room side a gas cabinet is provided with gas control components and optionally pressure control or vacuum components. Vertical furnaces for batch processing of substrates are preferably placed side by side, without any space in between the systems, to minimize the joint footprint of a plurality of systems. This implies that access to the system can only be provided at the front and the rear side and not via the sides.
A solution described in U.S. Pat. No. 6,332,898 (Tometsuka et al.) is that substrate cassette and wafer handling and storage components at the front side of the system are movable between a processing time position and a maintenance time position. When moved in a maintenance time position, the components can be accessed for maintenance from the front side of the system. The vertical furnace can be accessed from the rear side of the system.
However, the design proposed by US'898 has the disadvantage that all maintenance actions on the substrate cassette and wafer handling and storage components are performed in intimate communication with the clean room. E.g. if a wafer handling robot needs to be replaced, the broken robot and the replacement robot need to be transported through the clean room. Further, the substrate cassette handling and storage components and wafer handling components remain in the system and may hinder accessibility of other components. Further, a gas component cabinet is provided at the rear side of the system and this may hinder the accessibility of the vertical furnace when maintenance needs to be performed. During replacement of e.g. a quartz process tube, which is a large component, sufficient space needs to be available and the gas cabinet can be a significant obstacle.
With the transition to a wafer size of 450 mm all components grow in size and the space requirements become even stronger. For the handling of large components such as process tubes, flanges, heating elements etc. large tools are required that occupy a lot of space. A solution would be to place the gas cabinet remote from the vertical furnace with the disadvantage of long gas supply lines and control lines between furnace and gas cabinet.